1. Field of the Invention
The present invention relates to a power transmission device for a vehicle and is suitably used for a hybrid vehicle.
2. Description of Related Art
Conventionally, as a power transmission device used for a hybrid vehicle, there has been known a device described in Patent document 1 (JP-A-H09-123773). As shown in FIG. 1 of Patent document 1, the power transmission device has an engine input shaft 32, to which a power generated by an engine 51 is inputted, and a cylindrical first output shaft 33, to which second and fourth gears are attached. The power transmission device is structured such that the engine input shaft 32 and the cylindrical first output shaft 33 are engaged and disengaged by a first clutch 36. Also, the power transmission device has a cylindrical second output shaft 34, to which first and third gears are attached. The power transmission device is structured such that the engine input shaft 32 and the cylindrical second output shaft 34 are engaged and disengaged by a second clutch 37. A power generated by a motor 53 is also inputted to the second output shaft 34.
By employing such the construction, the engine 51 can use not only the second and fourth gears of the first output shaft 33 but also the first and third gears on the motor 53 side by engaging the second clutch 37. The motor 53 can use not only the first and third gears on the motor 53 side but also the second and fourth gears by engaging the first clutch 36 and the second clutch 37.
As described above, as a construction for increasing variations of gear selection, the power transmission device is structured such that the power can be transmitted from the engine input shaft 32 to the second and fourth gears and the first and third gears through the first clutch 36 and the second clutch 37 respectively. That is, the first to fourth gears can be commonly used by the engine 51 and the motor 53.
However, in the power transmission device of Patent document 1, it is necessary to provide the clutch 36 dedicated to a power transmission route from the engine input shaft 32 to the first output shaft 33 (second and fourth gears) and the clutch 37 dedicated to a power transmission route from the engine input shaft 32 to the second output shaft 34 (first and third gears) individually. Therefore, the number of the clutches is increased, and eventually an entire size of the power transmission device enlarges.